In-well monitoring and flow control system

ABSTRACT

An in-well monitoring and flow control system with an improved power supply is described. A separate high voltage ( 18 ) and low voltage power supply ( 23 ) is provided together with a cable ( 14 ) which has at least two separte cores; one core ( 24 ) for high voltage power and the other core ( 26 ) for low voltage power and control monitoring communications. Embodiments of the invention are described.

[0001] The present invention relates to control and monitoring systemsfor wells and particularly, but not exclusively, for hydraulic controlof downhole flow control systems. The invention also relates to anin-well power supply for use with an in-well flow control and monitoringsystem.

[0002] Control systems for providing hydraulic control of valves fromthe surface are known. One example is the PES “SCRAMS” system whichprovides electro-hydraulic control of in-well valves from the surface.This system has solenoids which are supplied at a voltage of 120 voltsfor operating valves at 3,000 to 4,000 psi. Other systems are based onusing electrical energy only to control valve operation and do notrequire hydraulic control. This means that a higher voltage, forexample, 400 DC is needed to generate sufficient power to operate thevalves. In practice, this is achieved by the use of a downhole powersupply system incorporating high power electronic components in thedownhole tool.

[0003] It is well known that downhole valves and monitoring systems haveto operate at high temperatures. Electronic components operating at hightemperatures are often prone to failure. This is because most normalelectronic components are designed to operate at temperatures well belowmost oil/gas well temperatures, and the mean time below failure (MTBF)of the components falls rapidly as the environmental temperature whichthe components are exposed to, exceeds the design temperature. Thisproblem is particularly acute where high voltage/currents are applieddue to high electrical stresses and the operation of additional localheat by the components.

[0004] In some existing systems the size of the cable, and theconductors within the cable also limits the power which can be suppliedto the cable and consequently increasing the power supply to thedownhole control system has been problematic. Increasing thecross-section of the cable can result in a much more expensive cable,which is difficult to obtain and to integrate with existing systems,which require a “standard” cable size to be used.

[0005] In addition, with existing systems there is a limit to the numberof devices or valves which can be driven from a single power supply. Thecurrent limit is about four to five devices and also the maximum powerwhich can be used with the electrical only supply is about 400 volts DC.This makes it difficult to use valves above a certain size which may berequired in a certain situation. Also, existing systems cannot power-upduring deployment for safety reasons which means that it is not possibleto monitor the downhole valves during deployment.

[0006] An object of the present invention is to provide an improvedcontrol and monitoring system for wells which obviates or mitigates atleast one of the disadvantages associated with existing systems.

[0007] A further object of the present invention is to provide animproved power supply for use with an in-well flow control system whichobviates or mitigates at least one disadvantage associated with existingpower supplies.

[0008] This is achieved by providing separate high voltage and lowvoltage power supplies and a cable which has at least two separatecores; one core for high voltage power and the other core for lowvoltage power and control monitoring communications.

[0009] This solution provides a number of advantages over theaforementioned prior art arrangements. Firstly, the maximum high powerwhich can be used is not limited to 400 volts; and the system can beused for up to 255 downhole devices. A further advantage is that voltagecan be varied at surface to suit the downhole hardware and the systemcan be powered up during deployment because the low voltage line can beused to continuously monitor what is happening downhole. A yet furtheradvantage is that the position of a downhole component such as a valvecan be monitored and high voltage power supplied to make furthermovements. The cable sheathing is used as the earth return in shallowerwells providing the advantage that a separate earth is not needed forshallower wells. A shallow well may be considered as one less than 4,000feet. However, for deeper wells, in excess of 4,000 feet, the resistanceof the armoured cable may be too high to provide a satisfactory returnpath and, in such a case, a cable with three cores is used; one for highvoltage power, one for low voltage and one for an earth return.

[0010] According to a first aspect of the present invention there isprovided an in-well flow control and monitoring system for controlling aplurality of electrically operable downhole elements from a surfacepower supply, said system comprising:

[0011] a high voltage power supply;

[0012] a low voltage power supply;

[0013] at least one high voltage downhole component and at least one lowvoltage downhole component;

[0014] a cable having at least two separate conductors and an earthreturn, a first conductor for coupling the high voltage power supply tothe at least one high voltage component and a second conductor forconnecting the low voltage power supply to the at least one low voltagecomponent, monitoring means coupled to at least one high voltagedownhole component for monitoring when a high voltage is required toactuate said downhole component, and means for supplying said highvoltage to said high voltage component in response to a signal from saidmonitoring means.

[0015] Preferably the earth return is provided by the cable sheathing.Alternatively the earth return is provided by a separate conductorwithin the cable so that said cable has three separate conductors; ahigh voltage power supply conductor; a low voltage conductor, and anearth return conductor.

[0016] Preferably, the high voltage power supply is greater than 400volts DC. Preferably the control and monitoring system can be addressedfrom the surface allowing a plurality of sensors and valve controllersto be coupled to the same conductor. This arrangement also allowsmultiple flow control devices to be coupled to the conductor carryinghigh voltage. Conveniently the flow control and monitoring system can beused to control up to 255 downhole elements, from said same conductorand supplied by same power supply.

[0017] Preferably also, the high voltage power supply can be varied atsurface to suit various downhole hardware.

[0018] Conveniently, said low voltage monitoring means for monitoringsaid high voltage downhole component is coupled to a position transducerfor monitoring the position of the high voltage downhole component.Conveniently the high voltage downhole component is a valve which has avalve element which is rotatable between an open and a closed position.Conveniently the transducer is an optical transducer for opticallymonitoring the position of said downhole valve element.

[0019] According to a further aspect of the present invention there isprovided a method of operating an in-well flow control system having aplurality of downhole low voltage components, said method comprising thesteps of,

[0020] providing separate high voltage and low voltage power supplies,

[0021] coupling said high voltage and low voltage power supplies torespective said downhole high voltage components and said low voltagecomponents over separate electrical conductors,

[0022] monitoring said high voltage components to determine therequirement for high voltage to be supplied and providing a monitoringsignal indicative of whether power is required, and

[0023] supplying high voltage to said high voltage downhole componentswhen said monitoring signal indicates high voltage is required.

[0024] Preferably the method includes the step of using the cable sheathas the earth return. Alternatively the method includes the step of usinga separate conductor within the cable as the earth return.

[0025] Conveniently, when the downhole component is a valve with a valveelement, the method includes the step of monitoring the position of thevalve element to determine the requirement for high voltage power to besupplied to said downhole component.

[0026] Preferably, also the method includes the step of providing avariable surface power supply for varying the power at surface to thedownhole high voltage and low voltage power supplies.

[0027] Preferably also, the method includes the step of continuouslymonitoring the position of the valve element using the low voltage lineduring deployment of the high voltage downhole component.

[0028] Preferably also, the method includes the step of scaling thesurface high voltage power supply on demand to increase power to itssaid high voltage downhole components.

[0029] According to a further aspect of the present invention there isprovided a power supply for use with an in-well flow control andmonitoring system, said power supply comprising:

[0030] a separate high voltage power supply;

[0031] a separate low voltage power supply;

[0032] a cable having at least two separate conductors, a firstconductor for coupling the high voltage power supply to high voltagecomponents disposed downhole, and a second conductor for connecting thelow voltage power supply to low voltage components disposed downhole.

[0033] Preferably said cable has a conductive sheath which is used as anearth return for shallower wells. Alternatively said cable has aseparate conductor which is used as an earth return for deep wells.

[0034] Preferably, said high voltage power supply is scalable and shouldprovide increased high voltages on demand. Conveniently also, said highvoltage power supply is variable at surface to vary the power suppliedto the downhole components.

[0035] According to a further aspect of the invention there is provideda monitoring system for simultaneous monitoring high data rate and lowdata signals from downhole sensors, said system comprising:

[0036] a high data rate system configuration;

[0037] a low data rate system configuration;

[0038] a cable for use by said high data rate configuration and said lowdata rate configuration, said cable comprising a conductive sheath, afirst conductor for carrying a low voltage supply and low data ratesignals, at least two second conductors for carrying a low voltagesupply and high data rate signals, the high date rate systemconfiguration having a surface control unit coupled to at least one highdata rate downhole monitoring system by said at least two secondconductors;

[0039] the low data rate system configuration having a surface controlunit coupled to at least one low data rate downhole monitoring nodesystem by said first conductor, said conductive sheath being an earthreturn for low voltage power supplies for the high data rate low datarate system configurations.

[0040] Preferably, the cable has three conductors and a conductivearmoured sheath.

[0041] These and other aspects of the invention become apparent from thefollowing description when taken in combination with the accompanyingdrawings in which:

[0042]FIG. 1 is a schematic block diagram of an in-well flow controlsystem for high voltage power distribution to a number of flow controldevices with feedback and monitoring in accordance with an embodiment ofthe present invention used for shallow wells;

[0043]FIG. 2 is a detailed view of an alternative cable to that shown inFIG. 1 with a separate earth return conductor for use with the system ofFIG. 1 in deeper wells and for use with simultaneous high data rate andlow data rate downhole systems, and

[0044]FIG. 3 is a schematic block diagram of a downhole in-well systemconfiguration for running simultaneous high data rate monitoring and lowdata rate monitoring using the cable of FIG. 2.

[0045] Reference is now made to FIG. 1 which depicts an in-well flowcontrol system, generally indicated by reference numeral 10, whichincludes a surface portion 12 connected by a cable 14 to a downhole node#1, generally indicated by reference numeral 16. It will be understoodthat, in this embodiment, node 16 is only one node of 255 nodes whichare connected to the surface portion 12.

[0046] The surface portion 12 has a 400 volt DC high voltage powersupply (HVPS) 18 which is used to supply current up to 5 amps powerdownhole electronics in the nodes 16, on surface/subsea interface card20 which are both coupled to a computer controlled data acquisition andcommand module (CCDACM) 22 which utilises Expro proprietary control andmonitoring software (MZS) and a low voltage power supply (LVPS) 23coupled to the interface card 20. The high voltage power supply 18 andsubsea interface card 20 are coupled via cable 14 to the node 16. Thesurface/subsea interface card provides low voltage power, usually lessthan 100 V, and routes commands from CCDACM 22 and data to the cable 14.The CCDACM unit 22 allows control of high voltage and low voltagesurface power supplies and sends commands to downhole addressable deviceand surface devices. The unit 22 acquires data feedback sent to thesurface from downhole devices. The cable 14 is a dual conductor cablewith an armoured sheath 17. One conductor 24 is used to carry highvoltage power supply signals from the power supply to the downhole motorand the other conductor 26 carries low voltage power and communicationssignals between the monitoring and sensing equipment and the interfacecard 20, as will be explained below. The armoured sheath 17 is used asan earth return for both the high voltage and low voltage lines becausein the embodiment of FIG. 1 the well is less than 4,000 feet deep sothat the resistance of the armoured sheath is low enough to provide asatisfactory current return path.

[0047] The downhole node 16 is coupled to a downhole flow controlcomponent which is a valve with a rotatable valve element (not shown).The node 16 includes a motor 28 for moving the valve element between anopen and a closed position. The motor 28 actuates the valve elementunder control of motor controller 30. The low voltage power supply 23 iscoupled to a Node Interface Manager (NIM) unit 32 which is an Exproproprietary modem for sending/receiving commands and data. The NIM unit32 is coupled to a node low voltage power supply 34 and to systemmonitoring submode devices #1, #2 to #n denoted by response numerals 36,38 and 40 respectively.

[0048] The high voltage power supply 18 is connected to the downholemotor 28 via the cable conductor 24. However, the high voltage powersupply 18 is only supplies power to the motor 28 when there is a need tomove the valve element. In this regard, the position of the valve ispredetermined by the motor controller and a signal from the motorcontroller 30 is sent when the motor 28 is to be moved. Similarly, asignal is sent to the interface card 20 indicating the position of thevalve element and the data acquisition and command module 22 sends asignal to the high voltage power supply 18 to supply high voltage powerto the motor 28 only when the valve requires to be moved. This meansthat high voltage is only supplied to the motor 30 when required andmeans that the downhole electronic components are not stressed bycontinuous application of high voltage, thereby minimising thelikelihood of component failure and making the power supply last longer.A further advantage of this arrangement is that a digital addressprotocol (e.g., Standard Modbus, IEEE Standard, PROFIBUS) is used. Alsohigh voltage power is supplied to respective valves only when requiredby these valves. This provides a more efficient system which permits asingle high voltage power supply to supply 256 downhole nodes.

[0049] Reference is now made to FIG. 2 of the drawings which shows analternative cable 14 a which has three conductors: one high voltageconductor 24 a, one low voltage conductor 26 a and a separate earthreturn conductor 27. This alternative cable is used for deeper wells,especially in excess of 4,000 feet because the resistance of thearmoured sheath 17 a may become too high for an effective return path.It will be appreciated that the high voltage power supply may be set atany suitable value, such as 250 volts, 400 volts or higher. The exacthigh voltage value can be selected to suit downhole hardware.

[0050] The alternative cable 14 a shown in FIG. 2 may be used in anotherapplication for providing a connection to surface for a simultaneoushigh data rate monitoring and low data rate monitoring downhole system.In this application conductor 27 carries a low voltage supply from thesurface, command signals from the surface and downhole data to thesurface. This is done at data rates generally less than 10kilobits/second which is suitable for pressure, temperature and flowsignals etc. Conductors 24 a,26 a are for use with high data ratesystems such as seismic systems and carry command and data informationbetween well sensors and the surface. Conductors 24 a,26 a also carry alow voltage supply from the surface. The conductive armoured sheath 17 ais used as the earth return for the low voltage system.

[0051] Reference is now made to FIG. 3 of the drawings which depicts aschematic block diagram of a system configuration for runningsimultaneous high data rate monitoring with low data rate monitoring.The system has a high data rate monitoring configuration for seismicdata etc. which comprises a high rate CCDACM 41 coupled to a low voltagepower supply 42. The high data rate signals and low voltage power arecoupled to a downhole seismic system 44 on conductors 24 a,26 a. The lowdata rate monitoring configuration is similar to that described abovewith reference to monitoring system of FIG. 1 and includes a low rateCCDACM 46 and an associated low voltage power supply 48 which is showncoupled to downhole node 50 by single conductor 27 which carries, asdescribed above, low voltage supply from surface, commands from thesurface and data from the sub-nodes to the surface. The node 50 has alow voltage node power supply 52, a NIM 54 and three sub-nodes 56,58 and60 coupled to the NIM 54. The sub-nodes contain monitoring devices suchas pressure transducers, flowmeters and temperature sensors forgenerating low voltage low data rate signals for sending to CCDACM 46.The sheath 17 a, shown in broken outline, is the earth return for thelow voltage supplies 42,48. The low voltage low data rate system may becoupled to additional downhole nodes, up to 255 nodes, depending on thecapacity of the power supply.

[0052] Various modifications may be made to the aforementionedembodiment without departing from the scope of the invention. Although adownhole valve element is used and driven by the high voltage powersupply, other downhole elements may be used, such as a pump or motor orthe like. A mixture of downhole elements, such as valves, pumps andother elements requiring relatively high current and voltage may beused. Similarly, a variety of sensors may be used to monitor theposition or other parameter of the downhole elements, such astemperature or pressure. Consequently, the downhole sensors may bepressure transducers, flowmeters, vibration sensors, seismic sensors,temperature sensors or the like. Although a single high voltageconductor and a separate single low voltage conductor are disclosed, itwill be appreciated that more than one high voltage conductor and morethan one low voltage conductor may be used, as long as there areseparate conductors for the high voltage and low voltage supplies.

[0053] The use of a cable with a single high voltage conductor and asingle low voltage conductor is generally sufficient and economic.

[0054] In the low voltage high data rate and low data rate applicationsa large number of respective downhole high data rate and low data ratenodes can be supplied from low voltage power supplies.

[0055] An advantage of the present invention is that an in-well flowcontrol system is provided which can be used to supply high voltagepower to up to 255 different downhole devices from a single power supplysource. The separation of the high voltage and the low voltage powersupplies enables standard components to be used with minimal voltagestress because high voltage is supplied to a downhole element such as avalve only when required, instead of being continuously supplied. Afurther advantage of this arrangement is that the system can be poweredup during deployment of valves, pumps and the like which allowscontinuous monitoring during deployment using the low voltage line. Afurther advantage of the arrangement is that the high voltage isscalable on demand to increase power up to about 600V or the voltagelimitation ability of the conductor. The system can easily be modifiedfor shallower or deep wells simply by changing the type of cable used.The use of a cable with separate conductors for low voltage and highvoltage also permits the cable to be used on other applications; toprovide simultaneous high data rate monitoring and low data ratemonitoring using low voltage power supplies and using the cable sheathas the power supply earth return. Thus a single cable type can be usedfor different applications.

1. An in-well flow control and monitoring system for controlling aplurality of electrically operable downhole elements from a surfacepower supply, said system comprising: a high voltage power supply; a lowvoltage power supply; at least one high voltage downhole component andat least one low voltage downhole component; a cable having at least twoseparate conductors and an earth return, a first conductor for couplingthe high voltage power supply to the at least one high voltage componentand a second conductor for connecting the low voltage power supply tothe at least one low voltage component, monitoring means coupled to atleast one high voltage downhole component for monitoring when a highvoltage is required to actuate said downhole component, and means forsupplying said high voltage to said high voltage component in responseto a signal from said monitoring means.
 2. A system as claimed in claim1 wherein the earth return is provided by the cable sheathing.
 3. Asystem as claimed in claim 1 wherein the earth return is provided by aseparate conductor within the cable so that said cable has threeseparate conductors; a high voltage power supply conductor; a lowvoltage conductor, and an earth return conductor.
 4. A system as claimedin any preceding claim wherein the high voltage power supply is greaterthan 400 volts DC.
 5. A system as claimed in any preceding claim whereinthe control and monitoring system is addressable from the surfacewhereby a plurality of sensors and valve controllers are coupled to thesame conductor.
 6. A system as claimed in claim 5 wherein the flowcontrol and monitoring system is used to control up to 255 downholeelements, from said same conductor and supplied by same power supply. 7.A system as claimed in any preceding claim wherein said low voltagemonitoring means for monitoring said high voltage downhole component iscoupled to a position transducer for monitoring the position of the highvoltage downhole component.
 8. A system as claimed in any precedingclaim wherein the high voltage downhole component is a valve which has avalve element which is rotatable between an open and a closed position.9. A system as claimed in any preceding claim wherein the transducer isan optical transducer for optically monitoring the position of saiddownhole valve element.
 10. A method of operating an in-well flowcontrol system having a plurality of downhole low voltage components,said method comprising the steps of, providing separate high voltage andlow voltage power supplies, coupling said high voltage and low voltagepower supplies to respective said downhole high voltage components andsaid low voltage components over separate electrical conductors,monitoring said high voltage components to determine the requirement forhigh voltage to be supplied and providing a monitoring signal indicativeof whether power is required, and supplying high voltage to said highvoltage downhole components when said monitoring signal indicates highvoltage is required.
 11. A method as claimed in claim 10 wherein themethod includes the step of using the cable sheath as the earth return.12. A method as claimed in claim 10 wherein the method includes the stepof using a separate conductor within the cable as the earth return. 13.A method as claimed in anyone of claims 10 to 12 wherein when thedownhole component is a valve with a valve element, the method includesthe step of monitoring the position of the valve element to determinethe requirement for high voltage power to be supplied to said downholecomponent.
 14. A method as claimed in anyone of claims 10 to 12 whereinalso the method includes the step of providing a variable surface powersupply for varying the power at surface to the downhole high voltage andlow voltage power supplies.
 15. A method as claimed in anyone of claims10 to 12 wherein the method includes the step of continuously monitoringthe position of the valve element using the low voltage line duringdeployment of the high voltage downhole component.
 16. A method asclaimed in anyone of claims 10 to 12 wherein the method includes thestep of scaling the surface high voltage power supply on demand toincrease power to its said high voltage downhole components.
 17. A powersupply for use with an in-well flow control and monitoring system, saidpower supply comprising: a separate high voltage power supply; aseparate low voltage power supply; a cable having at least two separateconductors, a first conductor for coupling the high voltage power supplyto high voltage components disposed downhole, and a second conductor forconnecting the low voltage power supply to low voltage componentsdisposed downhole.
 18. A power supply as claimed in claim 17 whereinsaid cable has a conductive sheath which is used as an earth return forshallower wells.
 19. A power supply as claimed in claim 17 wherein saidcable has a separate conductor which is used as an earth return for deepwells.
 20. A power supply as claimed in any one of claims 17 to 19wherein said high voltage power supply is scalable and should provideincreased high voltages on demand.
 21. A monitoring system forsimultaneous monitoring high data rate and low data signals fromdownhole sensors, said system comprising: a high data rate systemconfiguration; a low data rate system configuration; a cable for use bysaid high data rate configuration and said low data rate configuration,said cable comprising a conductive sheath, a first conductor forcarrying a low voltage supply and low data rate signals, at least twosecond conductors for carrying a low voltage supply and high data ratesignals, the high date rate system configuration having a surfacecontrol unit coupled to at least one high data rate downhole monitoringsystem by said at least two second conductors; the low data rate systemconfiguration having a surface control unit coupled to at least one lowdata rate downhole monitoring node system by said first conductor, saidconductive sheath being an earth return for low voltage power suppliesfor the high data rate low data rate system configurations.
 22. A systemas claimed in claim 21 wherein the cable has three conductors and aconductive armoured sheath.